It's hardly surprising that people with osteoarthritis of the knee are not as physically active as healthy adults in the general population. But experts say their high levels of inactivity, as reported in a recent study, are alarming.

In a study of 1111 adults with knee osteoarthritis, researchers found that 40.1% of the men and 56.5% of the women were inactive during a 7-day period when they wore accelerometers to monitor their activity. In fact, only 12.9% of men and 7.7% of women in the study met national guidelines for adults to get 2½ hours of moderate-intensity aerobic activity or 1 hour and 15 minutes of vigorous physical activity per week (Dunlop DD et al. Arthritis Rheum. doi:10.1002/art.30562 [published online ahead of print July 26, 2011]).